Bank customers who suffered knock-on costs during NatWest's IT meltdown will be reimbursed no matter who they bank with, its chief executive said today.

Royal Bank of Scotland Group boss Stephen Hester also promised free credit checks for people who fear their lending status may have been affected because of their inability to pay bills in the crisis last month.

In an open letter to users of the MoneySavingExpert website, Mr Hester said that while non-customers should contact their own bank to resolve their problems, anyone who has incurred extra charges will be reimbursed, whether they are RBS customers or not.

RBS Group is still clearing up the chaos caused by a computer failure three weeks ago, with Ulster Bank's problems lingering for longer than those of Royal Bank of Scotland and NatWest.

The group has so far cleared up 90% of 21,000 inquiries which could not be resolved immediately and needed further investigation.

Those who have lost money directly because of the problems can expect to recoup costs such as overdraft fees and interest, late payment
fees and interest on mortgages, loans and credit cards and missing interest on savings.

For those who have had to dip into an RBS Group isa, the bank can
manually reset its tax-free allowance to make sure customers are not disadvantaged.

If someone has been wrongly hit by charges from another major bank or building society, the other provider should refund the customer as an agreement is in place to treat people who have been affected sympathetically.

But RBS Group said it will reimburse any losses as a direct result of the crisis, if they are not refunded by another party, which includes those for non-customers as well as its own.

People have been urged to keep evidence of extra charges such as emergency travel tickets so they can prove how they were out of pocket.

Wrongly applied RBS/NatWest charges between June 19 and July 6 will be automatically refunded to customers, but people might need to make a claim for those after July 6, the banking group said.

The window for Ulster Bank customers is ongoing as the group is still trying to clear up the problems. It will write to customers detailing refunds by the end of the month.

If someone has had problems with their wages because their employer banks with RBS, this can be identified from the reference number on their bank statement, next to the entry detailing payments.

Mr Hester said: "Those who incurred extra costs will be reimbursed, whether they are our customers or not.

"We know there are customers of other banks who will have been affected and have worked closely with those banks to ensure they can resolve any such concerns. They should contact those banks about resolving their problems."

The failure left many customers unable to see or use cash paid into their accounts over the past few weeks, meaning people had home purchases delayed and holidays disrupted.

Fears have been raised that people might unknowingly have their credit scores blotted, but concerned customers will be able to get a special code to obtain a free online Experian report.

Mr Hester said: "We will ensure no customer's credit rating is affected as a result of this incident. We will work to set the record straight before any credit reports are supplied to Experian.

"And to give peace of mind, we're also writing to these customers with details of how they can receive a free credit check.

"The next step is to put things right for people who faced knock-on costs during the systems delay."

Mr Hester, who has said he will forgo his bonus this year because
of the problems, apologised again for the "unacceptable" delays.

He said: "This incident was a stark reminder of how our customers
rely on us every day. I am determined that we win back their trust.

"When we have finished the job of putting things right, we will also want to invite our customers to have a discussion with us about how
we can do things better in the future."

MoneySavingExpert.com creator Martin Lewis cautioned that many people will have lost far more cash than the obvious bank fees and charges, such as people who might have had to buy a new aeroplane flight.

He said: "I'd suggest all customers tot up their direct losses and if it isn't refunded directly, contact the bank and ask it for the money back, so keep receipts.

"This applies to affected non-customers too, such as those who didn't get paid because their firm banks with RBS."